ICD for REEF circular Encircled Energy calibration file. Parameter data cube HDU for PSF encircled energy. Version: 2008 Aug 25.

Transcription

1 ICD for REEF circular Encircled Energy calibration file Parameter data cube HDU for PSF encircled energy Contents Version: 2008 Aug 25 1 Introduction 2 2 PSF encircled energy file IMAGE HDU header BINARY TABLE header Coordinate systems

2 Parameter data cube HDU for PSF encircled energy 1 Introduction It is fairly common to have a data product which gives the value of some quantity or parameter versus a number of coordinates. A number of approaches are used to represent such data in FITS. Here were recommend use of multiple IMAGE HDUs together with tabular coordinates in binary table HDUs. Storing the data in IMAGE HDUs makes it easy for generic tools to visualize them. Note: in this document, we do not distinguish between encircled energy and encircled counts fractions; this needs to be fixed in a future rev. 2 PSF encircled energy file The PSF encircled energy data consists of parameters as a function of detector position, energy, and encircled energy fraction: f(ecf,theta,phi,e). Each such parameter corresponds to a 4-D IMAGE HDU. In the circular ECF file, there is a triple of such parameters: the best estimate radius and the 1-sigmalow and 1-sigma-high values of the radius. In the elliptical ECF file, there are further triples corresponding to each of the ellipse fit parameters and their errors. In each case, it is recommended that the image grid be the same for all parameters in the file, so that they can share the same coordinate system. The structure of the file is: (/data/jcm/sds/dp/ecf.new) dmlist ecf.new blocks Dataset: ecf.new Block Name Type Dimensions Block 1: RADIUS Image Real4(100x14x8x40) Block 2: RADIUS_SMIN Image Real4(100x14x8x40) Block 3: RADIUS_SMAX Image Real4(100x14x8x40) Block 4: WCS-TAB1 Table 1 cols x 1 rows Block 5: WCS-TAB2 Table 1 cols x 1 rows Block 6: WCS-TAB3 Table 1 cols x 1 rows Block 7: WCS-TAB4 Table 3 cols x 1 rows For an elliptical ECF file, extra image HDUs for different parameters would be added as needed. 2.1 IMAGE HDU header The following keywords will be used for the CXC PSF file IMAGE HDU headers. First, we list the CXC keywords describing the observing configuration and then the CALDB indexing keywords. 2

3 HDUCLAS1 RESPONSE dataset relates to instrument response HDUCLAS2 REEF2 HDUCLAS3 PREDICTED HDUCLAS4 NET ORIGIN CXC Calibration CREATOR write-ecf-fits 1.14 DATE T23:16:31 MODEL orbit_xrcf+tilts_04 raytrace configuration MISSION AXAF should you accept it TELESCOP Chandra satellite INSTRUME TEL DETNAM HRC-I GRATING NONE SHELL 1111 Shell 1346 bitmap FILTER NONE CCNM0001 CDES0001 CBD10001 CBD20001 CBD30001 CBD40001 CBD50001 CBD60001 CCLS0001 CDTP0001 CVSD0001 REEF2 HRMA Encircled Energy ECF( ) THETA( )arcmin PHI( )deg ENERG_LO( )keV ENERG_HI( )keV SHELL(1111) BCF DATA T02:57:00 BUNIT = arcsec / Units of Radius The actual example file has a more extensive header: SIMPLE = T / file does conform to FITS standard BITPIX = -32 / number of bits per data pixel NAXIS = 4 / number of data axes NAXIS1 = 100 / length of data axis NAXIS2 = 14 / length of data axis NAXIS3 = 8 / length of data axis NAXIS4 = 40 / length of data axis EXTEND = T / FITS dataset may contain extensions COMMENT = FITS (Flexible Image Transport System) format is defined in Astronomy / COMMENT = and Astrophysics, volume 376, page 359; bibcode: 2001A&A H / HDUNAME = RADIUS / ASCDM block name LONGSTRN = OGIP 1.0 / The HEASARC Long String Convention may be used. COMMENT = This FITS file may contain long string keyword values that are / COMMENT = continued over multiple keywords. The HEASARC convention uses the & / 3

4 COMMENT = character at the end of each substring which is then continued / COMMENT = on the next keyword which has the name CONTINUE. / HDUCLAS1 = RESPONSE / dataset relates to instrument response HDUCLAS2 = REEF2 / HDUCLAS3 = PREDICTED / HDUCLAS4 = NET / BUNIT = arcsec / Units of Radius CCNM0001 = REEF / CDES0001 = HRMA Encircled Energy / ORIGIN = CXC Calibration / CREATOR = write-ecf-fits 1.14 / DATE = T23:16:31 / MODEL = orbit_xrcf+tilts_04 / raytrace configuration MISSION = AXAF / should you accept it TELESCOP = Chandra / satellite INSTRUME = TEL / DETNAM = HRC-I / GRATING = NONE / CBD10001 = ECF( ) / CBD20001 = THETA( )arcmin / CBD30001 = PHI( )deg / CBD40001 = ENERG_LO( )keV / CBD50001 = ENERG_HI( )keV / CBD60001 = SHELL(1111) / CCLS0001 = BCF / CDTP0001 = DATA / CVSD0001 = T02:57:00 / SHELL = 1111 / Shell 1346 bitmap FILTER = NONE / HISTORY = write-ecf-fits / HISTORY = --config orbit_xrcf+tilts_04 / HISTORY = --denergy 0.5 / HISTORY = --detector HRC-I / HISTORY = --extract_order energy,theta,phi / HISTORY = --extract_re / HISTORY = ($RE{num}{real})[_/]($RE{num}{real})[_/]($RE{num}{real}).rdb / HISTORY = --flip_phi 1 / HISTORY = --frac fraction / HISTORY = --output hrmad hrci_ecf_n0002.fits / HISTORY = --rpar radius,arcseconds,radius_median,radius_p15.87,radius_p84.13 / HISTORY = --vdate T02:57:00 / CTYPE1B = ECF--TAB / Encircled fraction contour CTYPE2B = THET-TAB / [arcmin] Off Axis Angle CNAME2B = THETA / CUNIT2B = arcmin / CTYPE3B = PHI--TAB / [deg] Azimuth 4

5 CUNIT3B = deg / CTYPE4B = ENER-TAB / [kev] Energy CNAME4B = ENERGY / CUNIT4B = kev / PS1_0B = WCS-TAB / Table for lookup coord PV1_0B = 1 / Table for lookup coord PS1_1B = ECF / Column name PS2_0B = WCS-TAB / Table for lookup coord PV2_0B = 2 / Table for lookup coord PS2_1B = THETA / Column name PS3_0B = WCS-TAB / Table for PHI coord PV3_0B = 3 / Table for lookup coord PS3_1B = PHI / Column name PS4_0B = WCS-TAB / Table for lookup coord PV4_0B = 4 / Table for lookup coord PS4_1B = ENERGY / Column name CTYPE1P = ECF_BIN / CRVAL1P = 0 / CRPIX1P = 0 / CDELT1P = / WCSTY1P = PHYSICAL / CUNIT1P = bin / LTV1 = 0 / LTM1_1 = / CTYPE1 = ECF1 / CRVAL1 = / CRPIX1 = / CDELT1 = / CUNIT1 = / CTYPE2P = THETA_BIN / CRVAL2P = 0 / CRPIX2P = 0 / CDELT2P = / WCSTY2P = PHYSICAL / CUNIT2P = bin / LTV2 = 0 / LTM2_2 = / CTYPE3P = PHI_BIN / CRVAL3P = 0 / CRPIX3P = 0 / CDELT3P = / WCSTY3P = PHYSICAL / CUNIT3P = bin / LTV3 = 0 / LTM3_3 = / CTYPE3 = PHI1 / 5

6 CRVAL3 = 0 / CRPIX3 = / CDELT3 = / CUNIT3 = deg / CTYPE4P = ENERGY_BIN / CRVAL4P = 0 / CRPIX4P = 0 / CDELT4P = / WCSTY4P = PHYSICAL / CUNIT4P = bin / LTV4 = 0 / LTM4_4 = / CTYPE4 = ENERGY1 / CRVAL4 = / CRPIX4 = / CDELT4 = / CUNIT4 = deg / 2.2 BINARY TABLE header For each axis of the images we include a binary table with HDUNAMES WCS- TAB1,2,3,4. These HDUs contain single-row binary tables with vectors corresponding to the coordinate values. (I wish that WCS paper 3 had allowed column-oriented coordinate vectors instead of single-row-arrays, but we d better go with the standard). XTENSION = BINTABLE / binary table extension BITPIX = 8 / 8-bit bytes NAXIS = 2 / 2-dimensional binary table NAXIS1 = 400 / width of table in bytes NAXIS2 = 1 / number of rows in table PCOUNT = 0 / size of special data area GCOUNT = 1 / one data group (required keyword) TFIELDS = 1 / number of fields in each row EXTNAME = WCS-TAB / name of this binary table extension EXTVER = 1 / HDUNAME = WCS-TAB1 / ASCDM block name COMMENT = Coordinate lookup for axis / TTYPE1 = ECF / Coordinate TFORM1 = 100E / format of field TUNIT1 = / 2.3 Coordinate systems In the example file, I provide three different paths to the coordinate systems: 6

7 1. Standard FITS WCS for the ECF, PHI, ENERGY axes. These are useful for DS9 to be able to image the RADIUS data images and put coord values on them. THETA is not included since it s not regularly spaced. 2. FITS Paper 3 WCS-TAB keywords which allow modern, compliant FITS software (if any) to recognize the coordinate array HDUs as being the coordinates on the relevant axes. These keywords tie the PHI axis to the values in the lookup table HDU called WCS-TAB3. I recommend that CXC software should either use these keywords, or hard-code the lookups to the WCS-TAB HDUs for the ECF, THETA, PHI, ENERGY lookups. The ENERG LO and ENERG HI vectors are bin steps on ENERGY and have been included as separate arrays in the ENERGY bintable. It is to be hoped that a generic mechanism will eventually be provided to do this. The file ecf.new2 contains a 3D version of the ECF data, for ECF = 90 percent only. This file is easier to look at in DS9; each frame is a theta,phi map at a fixed energy, and using the cube play option you can cycle through the energies. We might consider using such small (50x smaller) derived files for applications where only one value of the ECF is going to be used. 7